Determining and/or providing said contour data set of a spectacle frame (also called eyeglass frame) rim is usually carried out in order to match to the frame the ophthalmic lenses to be mounted therein.
Devices have been developed to measure the contour of a spectacle frame. As for an example, contour follower devices which can “read” any shape such as the contours of rims or surrounds of any spectacle frame, for the purpose of trimming lenses to be fitted thereto, are widely used by eye care practitioners (ECP).
Contour follower devices generally use a feeler with a contact head to be applied to the article. Known contour follower devices comprise a support table fitted with holding means adapted to support the article whose contour is to be read off and the feeler is carried by a carriage which can reciprocate along a straight line path of the support, with rotation means for relative rotation between the support table and the carriage support. This type of contour follower devices provides a plurality of three dimensional points along a contour of a spectacle frame. These three dimensional measured points can be provided either using polar coordinates or orthogonal coordinates.
An example of a known contour follower device is disclosed in patent document U.S. Pat. No. 5,121,548.
Other means may be implemented to provide a plurality of three dimensional measured points along a contour of a spectacle frame, such as, for example, devices using laser measurements.
The plurality of three dimensional measured points along a contour of a spectacle frame is usually provided to a computer and used to calculate the edging parameter of ophthalmic lens to be manufactured for a given wearer and that would fit a chosen spectacle frame.
The present inventors have noticed that the raw three dimensional measured points provided by contour measurement devices may comprise singular points that can significantly affect the calculation of the edging contour of the final ophthalmic lens.
In some cases, the use of said singular points may lead to calculation divergence and thus to erroneous results.
There remains thus a need for improving the contour data set of a spectacle frame rim.